[clang] [clang-format] Fix a bug in SkipMacroDefinitionBody (PR #154787)

[via cfe-commits]

https://github.com/owenca updated https://github.com/llvm/llvm-project/pull/154787

>From 04dab5e8cf9646e88970350ee602cc82535322bc Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Thu, 21 Aug 2025 08:58:12 -0700
Subject: [PATCH 1/2] [clang-format] Fix a bug in SkipMacroDefinitionBody

Fixes #154683
---
 clang/lib/Format/UnwrappedLineParser.cpp | 9 ++++++---
 clang/unittests/Format/FormatTest.cpp    | 4 ++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 91b8fdc8a3c38..23938f8cb9d00 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1182,10 +1182,8 @@ void UnwrappedLineParser::parsePPDefine() {
   if (MaybeIncludeGuard && !eof())
     IncludeGuard = IG_Rejected;
 
-  if (FormatTok->Tok.getKind() == tok::l_paren &&
-      !FormatTok->hasWhitespaceBefore()) {
+  if (FormatTok->is(tok::l_paren) && !FormatTok->hasWhitespaceBefore())
     parseParens();
-  }
   if (Style.IndentPPDirectives != FormatStyle::PPDIS_None)
     Line->Level += PPBranchLevel + 1;
   addUnwrappedLine();
@@ -1196,6 +1194,11 @@ void UnwrappedLineParser::parsePPDefine() {
   Line->InMacroBody = true;
 
   if (Style.SkipMacroDefinitionBody) {
+    if (auto *Prev = Tokens->getPreviousToken(); Prev->is(tok::comment) &&
+                                                 Prev->NewlinesBefore > 0 &&
+                                                 !Prev->HasUnescapedNewline) {
+      Prev->Finalized = true;
+    }
     while (!eof()) {
       FormatTok->Finalized = true;
       FormatTok = Tokens->getNextToken();
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 83c664c3b81f3..1ef6877941c7d 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -26022,6 +26022,10 @@ TEST_F(FormatTest, SkipMacroDefinitionBody) {
                  "  A  a \\\n "
                  " A  a",
                  Style);
+  verifyNoChange("#define MY_MACRO          \\\n"
+                 " /* this is a comment */ \\\n"
+                 "   1",
+                 Style);
 }
 
 TEST_F(FormatTest, VeryLongNamespaceCommentSplit) {

>From efa660e867e7969e22ce21aa06197408df683068 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Thu, 21 Aug 2025 21:06:21 -0700
Subject: [PATCH 2/2] Cleanup

---
 clang/lib/Format/UnwrappedLineParser.cpp | 40 ++++++++++++++----------
 clang/unittests/Format/FormatTest.cpp    |  4 +--
 2 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 23938f8cb9d00..ca7e2da3799c4 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1191,28 +1191,34 @@ void UnwrappedLineParser::parsePPDefine() {
 
   Line->PPLevel = PPBranchLevel + (IncludeGuard == IG_Defined ? 0 : 1);
   assert((int)Line->PPLevel >= 0);
+
+  if (eof())
+    return;
+
   Line->InMacroBody = true;
 
-  if (Style.SkipMacroDefinitionBody) {
-    if (auto *Prev = Tokens->getPreviousToken(); Prev->is(tok::comment) &&
-                                                 Prev->NewlinesBefore > 0 &&
-                                                 !Prev->HasUnescapedNewline) {
-      Prev->Finalized = true;
-    }
-    while (!eof()) {
-      FormatTok->Finalized = true;
-      FormatTok = Tokens->getNextToken();
-    }
-    addUnwrappedLine();
+  if (!Style.SkipMacroDefinitionBody) {
+    // Errors during a preprocessor directive can only affect the layout of the
+    // preprocessor directive, and thus we ignore them. An alternative approach
+    // would be to use the same approach we use on the file level (no
+    // re-indentation if there was a structural error) within the macro
+    // definition.
+    parseFile();
     return;
   }
 
-  // Errors during a preprocessor directive can only affect the layout of the
-  // preprocessor directive, and thus we ignore them. An alternative approach
-  // would be to use the same approach we use on the file level (no
-  // re-indentation if there was a structural error) within the macro
-  // definition.
-  parseFile();
+  if (auto *Prev = Tokens->getPreviousToken(); Prev->is(tok::comment) &&
+                                               Prev->NewlinesBefore > 0 &&
+                                               !Prev->HasUnescapedNewline) {
+    Prev->Finalized = true;
+  }
+
+  do {
+    FormatTok->Finalized = true;
+    FormatTok = Tokens->getNextToken();
+  } while (!eof());
+
+  addUnwrappedLine();
 }
 
 void UnwrappedLineParser::parsePPPragma() {
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 1ef6877941c7d..136039d255393 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -26022,8 +26022,8 @@ TEST_F(FormatTest, SkipMacroDefinitionBody) {
                  "  A  a \\\n "
                  " A  a",
                  Style);
-  verifyNoChange("#define MY_MACRO          \\\n"
-                 " /* this is a comment */ \\\n"
+  verifyNoChange("#define MY_MACRO  \\\n"
+                 " /* comment */  \\\n"
                  "   1",
                  Style);
 }